In modern surgery, one of the most important instruments available to medical personnel is the powered surgical tool. One form of a powered surgical tool is a handpiece in which a motor is housed. Secured to the handpiece is a cutting attachment designed for application to a surgical site to perform a specific medical procedure. Some powered surgical tools are provided with drills, burs or reamers for cutting bores into tissue or for selectively removing tissue such as bone. Other motorized powered surgical tools are provided with saw heads. These tools separate large sections of hard and soft tissue. A wire driver is a power tool that, as its name implies, drives a wire into a patient, more particularly, a bone. Power tools are also used to perform other functions in the operating room. For example, it is known to use a power tool to mix the components that form a mass of surgical cement. Other powered surgical tools include power generating units such as ultrasonic drivers or devices that emit photonic (light) energy.
The ability to use powered surgical tools on a patient lessens the physical strain of surgeons when performing medical procedures on a patient. Moreover, most surgical procedures can be performed more quickly and more accurately with powered surgical tools than with the manual equivalents that preceded them.
One type of powered surgical tool that is especially popular with some physicians is the cordless, battery-operated powered surgical tool. As the name implies, this tool has a battery that functions as the power source for the tool power generating unit. This eliminates the need to provide the tool with a power cord connected to an external-power source. Elimination of the power cord offers benefits over corded, powered surgical tools. Surgical personnel using this type of tool do not have to concern themselves with sterilizing a cord so the cord can be introduced into the sterile surgical field or ensuring that, during a procedure, an unsterilized section cord is not inadvertently introduced into the surgical field. Elimination of the cord also results in the like elimination of the physical clutter and field-of-view blockage a cord brings to a surgical procedure.
There are differences between conventional power tools and power tools designed to perform surgical procedures. A power tool designed to perform a surgical procedure must be able to withstand the rigors autoclave sterilization. In an autoclave sterilization process, the tool is placed in a chamber in which the atmosphere is saturated with water vapor (steam) the temperature can exceed 110° C. and the pressure exceeding 290 torr. Internal components of the tool, including the electrical components of any circuit, if left unprotected in and repeatedly exposed to this environment, corrode.
One solution to prevent this type of corrosion is to housing as many electrical conductive components of the tool in sealed modules or sealed shells. The Applicant's U.S. Pat. No. 7,638,958/PCT Pub. No. WO 2007/002180A2, the contents of which are explicitly incorporated herein by reference by reference, discloses how many of the components associated with a motorized powered surgical tool can be incorporated into a single sealed module.
The assembly of the above publications does a more than adequate job of protecting many of the electrical components of a powered surgical tool from the adverse effects of sterilization. However, over time the joints of the sealed module can breakdown. Also, the motor, the rotor and windings, of this tool is not protected to the extent the components in the sealed module are protected. Further, it can be expensive to provide a tool with the protection provided by this sealed module.
Another solution to this problem is to divide the components of the tool into two parts, one that is sterilized and one that is not sterilized. More specifically, this type of tool includes a power module and a handpiece. The power module includes the power generating unit, for example a motor. Also disposed inside the power module are cells that store charge used to activate the power generating unit. The power generating unit includes a control circuit. The control circuit regulates the activation of the power generating unit. The body, the shell, of this power generating unit, as well as the components internal to the body, are not designed to withstand the sterilization process.
The second part of the tool is the handpiece. The handpiece includes a body or shell. Internal to the handpiece body is a void for receiving the power generating unit. A handpiece also includes some sort of transmission. The transmission is capable of transmitting the power output by the power generating unit to the attached implement that is applied to the patient to perform the desired procedure. Often the handpiece includes some sort of coupling components. The coupling components facilitate the releasable attachment of the implement to the transmission. The handpiece body and the attached components are designed to withstand the rigors of the sterilization process.
When a tool with an aseptic power module is prepared for use, the handpiece is sterilized. The power module is placed in the closed void internal to the handpiece. This seals the unsterilized power module from the environment around the patient. The tool is then used in the same manner in which a sterilizable tool is used. The power generating unit is actuated to cause the implement to perform the desired procedure on the patient.
A benefit of the above described type of tool is that only the handpiece and its internal components need to be designed to withstand sterilization. This makes it less expensive to provide this type of tool in comparison to a tool the whole of which is subjected to sterilization. Further, since the aseptic power module of this tool is not subjected to sterilization, there is no possibility that this module will, as a result of being exposed to the sterilization process, malfunction.
While the above type of tool is useful, there are limitations associated with the tool. Some of these limitations are due to the fact that many power surgical tools, while similar in shape, are different in operation. For example, two motorized powered surgical tools a surgeon may employ are a wire driver and a sagittal saw. Both tools include a motor. The tools are designed to drive different implements. The wire driver is designed to rotate a wire or a pin. A sagittal saw is designed oscillate a blade back and forth in plane around an axis that extends through the plane in which the blade moves. Difficulties can arise if one inadvertently place a power module designed for use with the handpiece of one of these tools into the handpiece of the other tool.
One suggested solution to this problem is to provide a switch on the power module. At one point during the process of assembling the tool for use is that the switch is manually set to indicate the type of handpiece to which the power module is coupled. A disadvantage of this solution is that it requires the individuals preparing the tool for use to properly set the switch.